1. Field of the Invention
The present invention relates to a displacement control device which uses a piezoelectric/electrostrictive element to operate so that a portion describes a hysteresis displacement locus. The present invention further relates to an actuator using the same device, applicable properly to mechanisms for adjusting displacement, position and angle of various types of precision parts and others of optical equipment, precision equipment and other apparatus. The present invention is further employable for rotating motors, linear conveying apparatus, or the like.
2. Description of the Related Art
In recent years, in the fields of optics, magnetic recording, precision processing and others, a request for a displacement device or an actuator, capable of adjusting an optical path length or a position on the order of submicron, has come into existence. Additionally, fine machining techniques for micromachines have been actively studied, and power parts, such as motors, have become the center of wide interest in the medical field for local operation or the like.
Moreover, parts used in various types of electronic equipment have advanced rapidly in size and weight reduction, and conveying machines, parts feeders and others used for conveying or selecting such parts must also be suitable with respect to the configuration requirements to achieve high-accuracy.
So far, electromagnetic motors have come into widespread use as the foregoing actuator or the like. However, the control based upon the electromagnetic motor does not reach very high accuracy. For this reason, when employed in displacement control apparatus, in many cases, the electromagnetic motor takes charge of rough movement, whereas final fine movement (positioning) relies upon the use of a device equipped with another displacement mechanism. Further, the electromagnetic motor involves an undesirably large power consumption.
An example of a new technology related to the electromagnetic motor is an electrostatic type microactuator produced according to a Si or Ni micromachine process in Preliminary Reports xe2x80x9c1997 International Conference on solid-state Sensors and Actuatorsxe2x80x9d p1081-1084 of xe2x80x9cTRANSDUCER ""97.xe2x80x9d This offers micro-displacement by applying a voltage to and among a plurality of plate-like electrodes formed by a micromachining technique.
A problem arises with this actuator, however, in that difficulty in increasing the proper frequency because of its structure is experienced, so that the vibration is originally hard to attenuate at high-speed operation, which in turn increases the manufacturing cost for the micromachining process itself. With respect to a displacement control apparatus using such an actuator, further improvement in drive accuracy and in cost is desired.
Accordingly, the present invention has been developed in consideration of the foregoing problems associated with various types of actuators, and it is an object of the invention to provide a displacement control device capable of precise operation at high speed but at low power, and further, to provide an actuator having a plurality of identical displacement control devices.
For this purpose, in accordance with this invention, a displacement control device is provided, comprising a substrate, two diaphragms joined to at least side surfaces of a recess section made in the substrate, and a connecting plate put between the two diaphragms and joined to a bottom surface of the recess section, so that at least one end portion of each of the two diaphragms is joined to the connecting plate and an opposite end portion thereof is joined to the substrate. Further, at least two independent piezoelectric/electrostrictive elements are located at both the diaphragms to, and the connecting plate is driven to create a hysteresis displacement locus. In this case, it is preferable that this displacement control device has a construction in which a fixing plate is joined to one end of the connecting plate.
In addition, in accordance with this invention, a displacement control device is provided, comprising a substrate and two diaphragms joined to at least side surfaces of opposing recess sections made in the substrate. The displacement control device also includes a connecting plate having one end portion in a lengthwise direction sandwiched between at least the two diaphragms, and having another end portion in the lengthwise direction being sandwiched between at least two different diaphragms. The connecting plate is placed to span between bottom surfaces of the recess sections, so that at least one end portion of each of the four diaphragms is joined to the connecting plate and an opposite end portion thereof is joined to the substrate. The displacement control device further includes a fixing plate having a lengthwise direction parallel to the direction in which the said connecting plate is sandwiched between the diaphragms. At least two independent piezoelectric/electrostrictive elements are located proximate the two diaphragms between which the connecting plate is sandwiched, at one end portion of the connecting plate, such that the fixing plate is driven to create a hysteresis displacement locus.
In the displacement control device where the fixing plate is used as an indispensable component, it is preferable that a notch portion is made in a joined portion between the fixing plate and the connecting plate. Additionally, it is also preferable that the connecting plate is divided into at least two sections in the lengthwise direction of the fixing plate and the fixing plate is joined to the at-least-two connecting plate sections. Furthermore, it is also acceptable that a hinge section is set on the fixing plate to extend along the lengthwise direction of the fixing plate from the junction between the fixing plate and the connecting plate.
In each of the above-described displacement control devices, it is also preferable that the connecting plate and the diaphragms are formed to be joined to each other at their side surfaces, and that the connecting plate, the diaphragms and the substrate are integrated with each other. Naturally, in the case of the installation of the fixing plate, the fixing plate can also be integrated therewith. Such an integrated construction is producible using a green sheet laminating technique.
In the displacement control device according to this invention, in addition to the piezoelectric/electrostrictive elements for driving, one or more piezoelectric/electrostrictive elements to be employed as auxiliary elements are desired. This case does not require that the driving piezoelectric/electrostrictive elements are identical in type to the auxiliary elements. Additionally, if the piezoelectric/electrostrictive elements and electrode leads conducting to electrodes of the piezoelectric/electrostrictive elements are coated with an insulating layer made of a resin or a glass, the durability is desirably improved. In this case, preferably, the resin is a fluororesin or a silicone resin. Moreover, preferably, a shield layer made of an electrically conductive material is formed on the surface of the insulating layer, which contributes to the improvement and stability of the drive characteristics.
Suitable materials for the substrate, the connecting plate and the diaphragms, include fully stabilized zirconia or partially stabilized zirconia. Additionally, preferably, the configuration of any one of the fixing plate, the connecting plate and the diaphragms is trimmed by laser beam machining or mechanical machining for dimensional adjustment. Further, it is also preferred that the electrodes in the piezoelectric elements are processed by laser beam machining or mechanical machining to adjustment the available electrode area thereof
Moreover, this invention provides an actuator using the foregoing displacement control device. That is, an actuator is provided having a plurality of displacement control devices each driven by two or more independent piezoelectric/electrostrictive elements so that a connecting plate or a fixing plate creates a hysteresis displacement locus. Preferably, the fixing plates are disposed so that their center lines run substantially parallel with each other, and/or the connecting plates are disposed so that their center lines run parallel with each other. Further, an actuator is provided having a plurality of displacement control devices located proximate the circumferential section of the connecting plate, and each is driven by two or more independent piezoelectric/electrostrictive elements so that the connecting plate or a fixing plate creates a hysteresis displacement locus.
In these cases, preferably, the plurality of displacement control devices are disposed so that the center lines of the fixing plates or the connecting plates intersect with each other and tip portions of the fixing plates or the connecting plates are directed to the intersection of the center lines of the fixing plates or the connecting plates.